Russian and Chinese naval forces stepped up maneuvers in the Western Pacific in June as their respective summertime training plans moved into high gear, according to Japanese government reports.

Newsweek's map shows Russian and Chinese ships making frequent use of sea lanes near Japan, a close U.S. ally, including the straits of Miyako, Osumi and Tsushima in the southwest and the Tsugaru and La Perouse straits in the north.

Japan disputes territories with Russia—the Kuril Islands in the Sea of Okhotsk—and with China—the Senkaku Islands the East China Sea—and shares maritime borders with a potential adversary in Kim Jong Un's North Korea.

Collectively, the strategic waterways throughout its archipelagic territory form part of the so-called first island chain, a Cold War-era defense strategy that sought to blockade the Soviet and Chinese navies at choke points as they attempted to transit U.S.-friendly territory into the expansive waters of the Pacific Ocean.

Regular disclosures by the Joint Staff Office within the Japanese Defense Ministry roughly trace the movements of both countries' warships, which typically are shadowed and photographed by Japan's Maritime Self-Defense Force vessels and aircraft.

In June, the Joint Staff Office said the Japanese navy intercepted 14 Russian and Chinese flotillas, a total of 27 vessels, as well as four fleets in May and seven in April, the first month of the financial year 2024.

Russian warships detected near its shores included the Udaloy-class destroyer Admiral Panteleyev and the Ropucha-class landing ships Oslyabya and Peresvet—all with Russia's Pacific Fleet—which sailed into the Western Pacific on June 18 via the Tsugaru Strait.

On Friday, Tokyo said China's Luyang-III class destroyer Kaifeng and Jiangkai-II class frigate Yantai—assigned to the country's North Sea Fleet—returned to the East China Sea the previous day from maneuvers in the Western Pacific.

The pair of warships had been spotted sailing in the opposite direction through the Osumi Strait, south of Japan's southernmost main island of Kyushu, on June 26.

Russia's Pacific Fleet is headquartered in the closed town of Fokino on the Peter the Great Gulf in the Sea of Japan. China's East Sea Fleet is located in Ningbo and its North Sea Fleet in Qingdao, two port cities on its east coast.

None of the Russian or Chinese ships was accused of violating Japanese territorial waters.

Russia and China's navies last drilled together in March in an event involving Iran. Last July, the two militaries held joint exercises that involved a significant naval component, with flotillas of warships sailing thousands of miles from the Sea of Japan into the Western Pacific, partially encircling Japan in the process.

The neighbors are expected to dispatch navy ships to the same waters in the coming weeks in what is considered a growing strategic alignment between Beijing and Moscow.

Separately on Friday, Russia's Pacific Fleet concluded 10 days of maneuvers in the region, deploying 40 vessels, fighter aircraft and helicopters as part of the training event.

The Russian and Chinese defense ministries could not be reached for comment after hours.